This is a request for funds to replace obsolete x-ray diffraction equipment which is indispensable for NIH supported studies of the mechanism of biologic mineralization (DE-04141), the characterization of bone mineral during fracture healing (AM-19776), and the ultrastructural characterization of biologic mineral (AM-18412). Characterization of normal and pathologic mineral deposits by x-ray diffraction using this equipment is also a part of the research performed by orthopaedic residents in the NIH supported training program (AM-07281).